The present invention relates to a vacuum adsorption hand for use with a material handling machine, for example, on the arm of a material-handling robot, to handle a material.
Further, the invention relates to a composite hand mechanism for an industrial robot, which hand mechanism includes means attachable to the wrist portion of the arm of the robot. Likewise, the hand is attachable to, for example, a manipulator, a crane, or other such apparatus for adsorbing and grasping a material.
Various types of apparatus such as robots, manipulators, fork lifts, trucks, cranes, and the like have served as material handling machines. Such apparatus are provided with means such as "hands" to hold or grasp a material or an article; the hands are connected to the apparatus. Generally, these hands are classified as fingerless types and types having fingers adapted to grasp a material. The fingered hands for example, pinch, sandwich, grasp, or likewise grip the material. Fingerless hands generally fall into two categories, those that hold a material by adsorption and those that receive material. Further, hands of the adsorbing type are classified as vacuum types or magnetic types.
Many of the hands having fingers use a system in which claws are inserted from the side portions of a material into the material to thereby sandwich the material. The material is then lifted and/or moved. This presents a problem in that when many articles are to be stacked adjacently, they cannot be stacked without a gap. In the case of conventional adsorption type fingerless hands, however, components such as arms or the like are not present on the sides of the hand. Therefore, many articles can be adjacently stacked.
Accordingly, adsorption type hands have been used for adjacently stacking materials or removing materials from stacks. Where the material was not adsorbable by magnetism, a vacuum type adsorption hand was used.
In general, a vacuum type adsorption hand is formed with a vacuum chamber in communication with a vacuum source. The upper surface of a material is adsorbed by the vacuum chamber. By moving the hand and an arm of an industrial robot together with the adsorbed material, the material can be loaded or unloaded, for example, or otherwise moved.
Once the material has been moved, the material can be released from the arm simply by introducing air into the vacuum chamber of the hand. According to the procedure, only the upper surface of a material is adsorbed. This presents advantages in that the loading work by the adsorption hand can be simplified. Also, the structure of the hand itself can be simple. Moreover, the adsorbing force is relatively large so that even fairly heavy materials can be safely moved.
A packaged material or article, wrapped in a plastic film or the like, presents special problems for conventional adsorption hands. Air suction ports are provided in the vacuum chamber to maintain the vacuum in the chamber. However, when a film or the like adheres over the air suction ports and closes the ports, the necessary vacuum condition for adsorption cannot be maintained. As a solution to this problem, a method has been considered in which the vacuum chamber is covered by a perforated metal or a wire net. However, in the case of the perforated metal, although direct obstruction of the air suction ports is prevented, the holes in the metal plate are closed by the plastic film or the like. On the other hand, the adsorbing force to adsorb a packaged material is determined by the total area of the holes formed in the perforated metal and the remaining surface, other than the holes, provides no adsorbing force and is dead space. Given such dead space, an adsorbing surface having a large area is needed to obtain a desired adsorbing force, whereby the size of the hand must be increased. This likewise is problematical.
Further, conventional adsorption hands are disadvantageous in that although their holding force by adsorption in the vertical direction is large, the holding force in the horizontal direction is small. Thus, when a force in the horizontal direction acts on the material held, the material may be separated from the adsorption pad of the hand since the adsorbing force in the horizontal direction is relatively weak. In addition, although the adsorbing force of the adsorption type hand is strong, in order to more safely perform the task of moving the material, a mechanical means which is certain to grasp the material is required.